Lean Phase Conveying Systems – A Batch Hopper Case Study

Blo-Tech Ltd. specialise in pneumatic conveying and mechanical handling systems for the bulk material handling industry. We have recently designed and manufactured a bespoke 8 m³ batch hopper for a pharmaceutical client that utilises both a lean and medium phase vacuum conveying system to fill and then discharge the batch hopper.

The hopper has a flanged connection to which a detachable, inspectable, reverse-jet-cleaning filter is mounted. This filter allows for the air used to convey the silica powder into the hopper to be released cleanly back into the atmosphere or out of the plant as required, whilst achieving a high separation efficiency.

Three 1000 kg load cells are provided to robust foot supports to allow the mass of the silica powder contents to be weighed. A control system is then used to switch a pneumatic butterfly valve to open, and again to close when the hopper has discharged a specified mass as fed-back from the load cell data. A controlled batch of powder is released, into the suction lean phase system at the outlet of the hopper, which transports the powder to a process mixer to be used in the correct quantity in the client’s recipe.

The powder is gravity fed into the suction system and silica can have a tendency to hold up in the hopper, therefore, dual vibrator motors as well as aeration pads were incorporated into the design of the hopper to aid discharge. The hopper cone was designed to have sufficiently steep sides to also minimise build-up of silica and ensure powder flow from the hopper.

Further design considerations included having extra flanged connections at the top of the hopper to enable the connections of a pressure relief rupture disk and high-level probe, plus a man-way entrance. The cone of the hopper was made in two parts, connected by a flange to enable the lower segment of the cone to be disconnected. This provides a man-way sized opening at the bottom of the hopper, as required for future cleaning and maintenance.

Lifting and weigh calibration plates were also incorporated into the design for ease of installation, calibration and commissioning. A stiffening ring ensures the hopper will withstand the pressures it will be subjected to – both positive pressure and high vacuum.

The hopper has been designed to a high standard providing an internal 2B plate finish and polished 240 grit external finish, with full penetration continuous welds. As the hopper was to be used within the pharmaceutical industry a thorough cleaning before sealing was also undertaken by the engineering team to ensure that the hopper could be installed straight into the factory location with minimum disruption to existing production for the client.

If you have the need for a similar system, Blo-Tech Ltd can design one, sized and equipped to meet your specific batch size requirements and material (e.g. explosion protection for potentially explosive materials, or discharge aids for poor flowing materials etc.), so contact us now via email at sales@blotech.co.uk or phoning +44 (0) 1932 854756. Blo-Tech Ltd can design and size complete lean and dense phase systems incorporating mechanical conveying solutions where required.